Welcome! We hope you enjoy following the restoration process of a 1918 Curtiss JN4D Jenny.
Once completed, the aeroplane will be flown and displayed at the Candler Field Museum in Williamson GA (30 miles south of Atlanta).
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Friday, March 26, 2010

Control Stick Torque Tube

What a busy week - work picked up and the kids had a big baseball tournament - so it felt good to get back to the hangar today.

Since the stick pedestal castings arrived, the next thing that had to be fabricated was the torque tube. No original Curtiss drawing exists for the torque tube, so Doc Hood hand drew one for me from scratch and I was grateful.

The torque tube has a 12 in. radius bend in the middle so the tube clears the rear rudder bar. It's a pretty stout bar - 1 1/8 in OD and .095 thickness. That's pretty thick!

The first step was to make templates for the inside and outside of the bend. I also transferred the Doc Hood drawing onto a piece of plywood.

Now the fun part. I've tried a lot of ways to bend tubing - filling the tube with sand, using a die roller etc. But Paul Dougherty told me he bends all his tubing with heat alone and I found his method works best...if you are patient!

Here is what I mean.

Heat the top of the bend until three or four inches are nice and red. Then heat the bottom of the bend the same way. Do not heat anything else.

See, heating the tubing makes the metal pliable. You want the top of the bend to stretch and the bottom of the bend to compress. You want to keep the sides cool (relatively speaking) so the tube will not kink! It really works.

Anyway, Keep alternating the torch between the top and the bottom while pulling on the end of the tube.

Here you can see the results of the process. Notice how the tube started to curve nicely. The left side has been worked and I was using the template as a guide. You want to "drag the hot spot" or simply heat an area until it bends a little then move further down the line.

See the heat marks extend the entire length of the curve. "Drag the hot spot". It takes some time to work this. Don't be in a hurry. Heat a little area at a time.

Here is the 12 in. radius when compared to the plywood template. At the end of the radius, the tube bends the other way. I bent the right side back to level using the same method above, but before I had time to bend the other end, it was time to pick up the kids at the bus stop. I'll post a picture of it next time.

John Gaertner sent me pictures of the ailerons. As with the wings, his workmanship is first class.

Chet Peek sent me these pictures last week. They are not Jennies, but since I really like seeing pictures from the Barnstorming era, I thought you might like to see them too. Anyway, Chet wrote:

These pictures show the Hisso powered J-1 Standards that were sent to Call Field in Wichita Falls TX and used for photographic training. They had to get to 7000 feet to get photographic coverage, and the Jenny wouldn't make it

But here is some mystery. The order, placed in December 1917 states they were Standard JR-1's, but they are clearly not. They have the regular J-1 gear and have a Hisso, not a 6-cylinder A-5 Hall-Scott which was used on the JR-1's.

So here we have a beautifully designed Hisso powered J-1 which did well according to the few pilot reports I could find. And yet they continued with the somewhat troublesome Hall-Scott A-7a.

Chet is writing a book about the Standard J1. I hope he saves me an advanced copy.

Also came across this old picture of three Jennies at Kelly Field. I forgot where the picture came from, but it's a neat photo and I wanted you to see it too.